BACKGROUND: Influenza A & B viruses are important human respiratory pathogens that cause seasonal influenza epidemics and periodic outbreaks worldwide. In Central America and the Caribbean, most of the currently-used seasonal influenza vaccines combine two influenza A strains and one influenza B strain into Trivalent Influenza Vaccines (TIVs). The reported effectiveness of TIVs can vary substantially with the level of match/mismatch between the vaccine strains and the prevailing influenza strains. Here, we aim to describe the gap of knowledge of influenza virus-type circulation, clinical features and potential B-lineage mismatch with vaccine strains in Central America.
METHODS & MATERIALS: Database from the Gorgas Commemorative Institute for Health Studies Influenza Program for Panama was examined retrospectively from 2010 to 2016. Demographics data, A-virus type and subtype and B-strain lineage, and clinical features and outcomes were collected. The percent level of mismatch between circulating and vaccine-recommended B-strain lineage was assessed for each seasonal year. Data presented here is preliminary as the final confirmed datasets are expected shortly from the ICGES.
RESULTS: Preliminary Results: A total of 1,592 respiratory samples from Panama were laboratory confirmed for seasonal influenza of which 83% and 17% were type A and type B, respectively. Type B strains circulated 5 out of the 7 years analyzed. The predominant lineage was Victoria but a switch to Yamagata was observed in 2014 (2010 B-lineage typing is pending). In 2015 and 2016, a mismatch between circulating and vaccine-recommended B-strain lineage was observed. The predominant age group affected by the influenza, overall and by subtype, is 0-4 years old. A higher percentage of older children were observed in the influenza B group (34%) compared to the influenza A- group (13%).
CONCLUSION: Due to unpredictable yearly virus co-circulation and B-lineage patterns, the recommendation of including both B-lineages in future vaccines remains important to reduce the burden of influenza disease.
